Samurai Jack is a young prince from medieval Japan whose father's empire is destroyed by the demon Aku. Jack escapes destruction and travels the world training his mind and his body for years, until he reaches adulthood. Then, taking his father's magic katana, he challenges Aku to a duel and defeats the demon. However, before Jack can deal the fatal blow, Aku creates a time portal and sends his opponent into the distant future, anticipating that he would be able to amass sufficient power to deal with the samurai later. The protagonist arrives in a hostile, futuristic Earth ruled by Aku and filled with his robot minions. The first people he encounters in the future call him "Jack" as a form of slang, which he adopts as his name.